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Heat conduction from basement to earth/soil below
Hi
I have a basement in my house. The floor is about 1.5m below earth/ground level and it is concrete about 30cm thick The floor is not insolated, so in order to save some money on the heating bill I am considering insolating it with sheets of polystyrene foam (in principle foam filled with air) with some rafters in a mesh to lay the wooden floor on. The lastly add 20mm of wooden plates/floor An architect has told me to break up the floor and lay a new one with 30cm of extra insolation But, I wonder if any of you guys can help me. I am an electrical engineer and I don't like to do this without calculating the needed insolation instead. My theory is that since the floor is 1.5m below ground level, the temperature of the soil will never be very cold. Searching the net I find something about 14degree celcius. So if I have 60square meters of floor heated to room temperature of 20degrees, how do I calculate the heattransfer when I have the data for the insulation and the concrete floor? Will the earth behave as an ideal giant block that has 6degrees of tempeature. So the gradient from the room temperature to the earth can never be higher than 10 degrees (20-14)? Numbers: Concrete, k = ~1W/mK Polystyrene, k = 0.03W/mK Wood, k = 0.14W/mK Power needed to keep temperature stable: P=KAT/D Concrete using 60square meters and 30cm thick: P = 1*60*6/0.3. P = 1.2kW Adding polystyrene: k = 0.042 , P = 0.03*60*6/0.05 = 216W The poystyrene is in parallel with the rafters. Assuming the rafters take up 5% of the floor instead of the polystyrene P= 0.14*60*0.05*6/0.05 = 50W So from these calculations it seems I need 250W to keep the room heated (not counting the walls) Any wrong doings in the calculations - comments? Thanks Klaus Kragelund |
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